The mechanism by which androgens and progestins regulate androgen action in mouse kindney will be studied. Specific progestins with known abilities to simulate, inhibit or enhance androgen action will be used. The kinetics, specificity and affinity of progestin binding and its effect on testosterone binding to the cytoplasmic androgen receptor and the characteristics of the steroid-receptor complex-nuclear interaction will be betermined. The subsequent stimuation of transcription, glucuronidase mRNA and specific proteins will be monitored. Plasma binding, celluar uptake and the kinetics, specificity and affinity of cytoplasmic and nuclear binding of 6alpha-mehtyl progesterone will be characterized to determine the factors involved in the enhanced uptake induced by excess unlabeled steroids in kidney but not in seminal vesicle nuclei. A new class of androgen-induced renal proteins, the T-proteins, which make up 1-3 percent of total protein when maximally induced, will be characterized. The T1 protein will be purified and a quantitative assay developed. A variety of inbred strains of mice will be screened for their T1 response to androgen. Our goal is to gain an in-depth understanding of androgen action and how it is regulated. The emphasis on progestin effects will provide data pertinent for contraceptive development. Overall it will further our understanding of steroid action and regulation in general.